Not with gas in it! You gotta get the fumes out as well. If not your project could be a blast.
If you are worried you can put water in it. I wouldn't, an empty clean tank is safe.
However BSA Bob is correct a body shop (father/son) wouldn't charge much to do it. pop out a couple of dimmples.

I have no faith in human perfectability. I think that human exertion will have no appreciable effect upon humanity. Man is now only more active - not more happy - nor more wise, than he was 6000 years ago. Edgar Allan Poe